1. Field of the Invention
The present disclosure relates to RNAi methods of pest management using oral delivery of polymeric/dsRNA nanoparticles to target insects.
2. Description of Related Art
RNA interference (RNAi) is a mechanism using double-stranded RNA (dsRNA) or small interfering RNA (siRNA) to trigger post-transcriptional gene silencing that destroys mRNA of a particular gene to prevent translation and the formation of an active gene product (most commonly a protein). The discovery of RNAi has not only provided a breakthrough in the methodology for functional analysis of genes, but also opened a novel avenue for treating human diseases and protecting crops against insect pest damages.
Although RNAi is a conserved mechanism in eukaryotes including fungi, plants, insects and mammals, there have been great challenges for successful RNAi in some organisms or some stages of an organism. Such difficulties may be attributed to the lack of effective delivery methods for dsRNA or siRNA, and the instability of these nucleic acids during and/or after the delivery. Currently, direct injection of dsRNA is the most commonly used delivery method for RNAi. However, injection has many drawbacks including: 1) it can be technically demanding and time consuming, 2) limitations exist in certain insect species (e.g., small size and aquatic living); 3) often lack of effectiveness in triggering RNAi, probably due to the absence of or inadequate cellular uptake of dsRNA in the larval tissues; and 4) limitations in the ability to inject a sufficient number of insects.
The success of RNAi is also largely determined by the stability of dsRNA or siRNA during and/or after the delivery. It has been reported that half-life for naked siRNA in serum ranges from several minutes to about an hour. Such a short half-life of the nucleic acids will not lead to an adequate RNAi response in an organism unless a high dose of dsRNA or siRNA is applied. To increase the stability of dsRNA or siRNA and enhance their cellular uptake, polymeric nanoparticles have been used for nucleic acid delivery in RNAi-based gene therapeutics.
There has been great interest and effort in mosquito research due to the significant impact mosquitoes have on human health and well-being in the world. In mosquitoes, RNAi is usually performed by injection of dsRNA during the adult stage. RNAi in mosquito larvae has not been well established due to their aquatic habitat and unavailability of effective dsRNA delivery systems for the larvae. Therefore, improved delivery methods for RNAi in mosquitoes and other insects are greatly needed.